1. Field of the Invention
The invention relates to a new process for the production of 4,4'-(phenylenediisopropyl)-bis(2,6-dialkylanilines) of the general formula: ##STR2## wherein R.sub.1 and R.sub.2 are the same or different and each is a (C.sub.1 -C.sub.4)-alkyl group, R.sub.3 is a hydrogen or halogen atom, and the central phenylene function is substituted in the 1,3 or 1,4 position, to 4,4'-(phenylene-1,3-diisopropyl)-bis(2,6-dialkylaniline) derivatives not yet described in the prior art and to the use of the mentioned bis-anilines as cross-linking agents for epoxy resins, as chain lengthening agent for polyurethanes, for the production of hydrolysis protective agents for polyurethanes and for the production of UV stabilizers in varnishes.
2. Background Art
A production method for 4,4'-(phenylenediisopropyl)-bisanilines is disclosed in Dutch Published Patent Application No. 6408539. The reaction of aniline, which is in great excess, with 1,4-diisopropenyl benzene in the presence of toluene or benzene as a solvent and activated alumina as a catalyst is described therein. In addition to the necessary large aniline excess, the very long reaction time of approximately 16 hours is a great drawback for an industrial process. Furthermore, the activated alumina catalysts are not well-defined compounds so that the reproducibility of the reactions is problematical.
Another variant for the production of 4,4'-(phenylenediisopropyl)-bis-anilines is disclosed in U.S. Pat. No. 3,200,152. As can be seen, especially from Example 5, the reaction of aniline with 1,3-diisopropylene benzene takes place in the presence of aniline-HCl in a reaction time of less than one hour at a very good yield of 92 percent. However, the tests of the present inventors have shown that this variant is unusable for the reaction of 2,6-dialkylanilines.